1. Field of the Invention
The present invention relates to a method for verifying data and a writing apparatus using charged particle beams, and more particularly to a method and apparatus for verifying writing data used for an electron beam writing apparatus.
2. Description of the Related Art
Lithography technique that advances microminiaturization of semiconductor devices is extremely important in that only this process forms a pattern in semiconductor manufacturing processes. In recent years, with an increase in high integration and large capacity of large-scale integrated circuits (LSI), a circuit line width required for the semiconductor devices is becoming narrower year by year. To form desired circuit patterns on these semiconductor devices, a master pattern (also called a mask or a reticle) with high precision is required. Then, the electron beam writing technique that has excellent resolution inherently is used for manufacturing such high precision master patterns.
FIG. 16 shows a schematic diagram illustrating operations of a variable-shaped type electron beam writing apparatus. As shown in the figure, the variable-shaped electron beam (EB) writing apparatus includes two aperture plates and operates as follows: A first or “upper” aperture plate 410 has a rectangular opening or “hole” 411 for shaping an electron beam 330. This shape of the rectangular opening may also be a square, a rhombus, a rhomboid, etc. A second or “lower” aperture plate 420 has a variable-shaped opening 421 for shaping the electron beam 330 that passed through the opening 411 of the first aperture plate 410 into a desired rectangular shape. The electron beam 330 emitted from a charged particle source 430 and having passed through the opening 411 is deflected by a deflector to penetrate part of the variable-shaped opening 421 of the second aperture plate 420 and thereby to irradiate a target workpiece or “sample” 340, which is mounted on a stage that is continuously moving in one predetermined direction (e.g. X direction) during the writing. In other words, a rectangular shape capable of passing through both the opening 411 and the variable-shaped opening 421 is written in a writing region of the target workpiece 340 mounted on the stage continuously moving. This method of writing or “forming” a given shape by letting beams pass through both the opening 411 and the variable-shaped opening 421 is referred to as a “variable shaping” method.
In performing electron beam writing, first a layout of a semiconductor integrated circuit is designed, and layout data (design data) for writing the design is generated. Then, the layout data is converted to generate writing data to be input into an electron beam pattern writing apparatus. The writing data is converted in the writing apparatus into shot data of a format used in the apparatus, to write each figure.
Generally, in order to enhance the data processing efficiency, a distributed processing is carried out, namely a writing region where patterns are arranged is divided into a plurality of small regions so that data can be distributed to each small region and data processing can be performed in each region. For example, a frame obtained by dividing the writing region into strip-like regions or a block obtained by further dividing the frame is used as a small region. A pattern is usually defined by one of the small regions to which the reference position of the pattern belongs. However, when it is necessary to arrange a pattern (ex. a cell) which extends over or “gets astride” small regions, if the pattern is defined by only one of the small regions which the pattern extends over, even if the distributed processing is performed, independency of the data processing of each small region will be deteriorated. Therefore, conventionally, the cell is previously divided not to protrude from the small region, to generate layout data. In that case, one cell is divided to be defined by each small region. Thus, two or more data is needed for the cell. As a result, there is a problem that the amount of layout data increases.
When there is a cell which can be formed by an array structure and a part (or all the elements) of the cell extends over another small region, it is normally supposed to take the following countermeasures. That is, an array development needs to be performed so that each cell may be defined by each small region in which the cell is to be arranged. Therefore, two or more data concerning the cell is needed, and thus the amount of layout data increases.
If the amount of layout data, especially at the upstream side, increases in the data conversion processing as stated above, time required for the conversion will increase when converting from the layout data into writing data. Furthermore, there is another problem that time required for transmitting the data to the next processing apparatus becomes huge amount of time. While an amount of data increases with the high integration of LSI in recent years, such data amount increase at the upstream side will affect throughput of the pattern writing apparatus.
As to a pattern aside subfields obtained by dividing the main deflection region, which has the same width and angle as those of a frame, into further smaller regions, the following technique is disclosed: that is, converting a boundary position of a subfield on the basis of a pattern extending over the subfields so that the pattern may not extend over them (refer to, e.g., Japanese Unexamined Patent Publication No. 11-67648 (JP-A-11-67648)).
As mentioned above, in order to enhance the independency of data processing of each small region, when arranging a pattern (ex. cell) extending over small regions, it is needed to previously divide the cell not to protrude from the small region, to generate layout data. Therefore, as mentioned above, there is the problem that the amount of layout data increases. Regarding the increase of the data amount, it is preferable that the amount of data increases in a latter step as late as possible. Then, the method described below, which is not disclosed to the public, is attempted to solve this problem.
In this method, a cell extending over small regions is not cut in the generation step of layout data. Instead of cutting, when converting writing data inputted in a writing apparatus into data of a format used in the writing apparatus, data of the pattern extending over small regions is copied to the small region which is extended over by the pattern, and a pattern portion which cannot be deflected in its own small region of the pattern extending over small regions is deleted. By this method, the cell extending over small regions can be distributed to each of the small regions, in the pattern writing apparatus. As a result, it becomes unnecessary to perform dividing data in the state of layout data or writing data. By virtue of this structure, increasing the data amount can be postponed to the stage of the writing apparatus, which is the downstream side of the data processing, not at the stage of layout data. Therefore, the efficiency of the distributed processing at the upstream side can be improved. Moreover, independency of distributed processing of each small region can be enhanced in the data processing stage in the pattern writing apparatus.
In this case, if cells defined by a plurality of small regions do not exist at the same coordinates in the absolute coordinate system, it may cause writing errors, such as a pattern omission and a pattern multiple exposure. For example, when configuring a cluster as a new section in the cell, the following problem arises. When data processing in the cluster is performed in a small region to which the starting point of the cluster belongs, if the absolute coordinate systems of the cells multiply defined are not in accordance with each other, it may cause a cluster omission or a cluster multiple processing. As a result, the writing errors, such as a pattern omission and a pattern multiple exposure stated above may be generated.
Thus, a method for verifying data is expected to prevent writing errors caused by the absolute coordinate system of the cell copied in the data conversion step being shifted or by distribution leakage indicating not being copied from the first. Moreover, it is expected to reduce verification time even in performing the verification. However, such a method for verifying data has not been established yet.